1//===--- ExprClassification.cpp - Expression AST Node Implementation ------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file implements Expr::classify. 11// 12//===----------------------------------------------------------------------===// 13 14#include "clang/AST/Expr.h" 15#include "clang/AST/ASTContext.h" 16#include "clang/AST/DeclCXX.h" 17#include "clang/AST/DeclObjC.h" 18#include "clang/AST/DeclTemplate.h" 19#include "clang/AST/ExprCXX.h" 20#include "clang/AST/ExprObjC.h" 21#include "llvm/Support/ErrorHandling.h" 22using namespace clang; 23 24typedef Expr::Classification Cl; 25 26static Cl::Kinds ClassifyInternal(ASTContext &Ctx, const Expr *E); 27static Cl::Kinds ClassifyDecl(ASTContext &Ctx, const Decl *D); 28static Cl::Kinds ClassifyUnnamed(ASTContext &Ctx, QualType T); 29static Cl::Kinds ClassifyMemberExpr(ASTContext &Ctx, const MemberExpr *E); 30static Cl::Kinds ClassifyBinaryOp(ASTContext &Ctx, const BinaryOperator *E); 31static Cl::Kinds ClassifyConditional(ASTContext &Ctx, 32 const Expr *trueExpr, 33 const Expr *falseExpr); 34static Cl::ModifiableType IsModifiable(ASTContext &Ctx, const Expr *E, 35 Cl::Kinds Kind, SourceLocation &Loc); 36 37Cl Expr::ClassifyImpl(ASTContext &Ctx, SourceLocation *Loc) const { 38 assert(!TR->isReferenceType() && "Expressions can't have reference type."); 39 40 Cl::Kinds kind = ClassifyInternal(Ctx, this); 41 // C99 6.3.2.1: An lvalue is an expression with an object type or an 42 // incomplete type other than void. 43 if (!Ctx.getLangOpts().CPlusPlus) { 44 // Thus, no functions. 45 if (TR->isFunctionType() || TR == Ctx.OverloadTy) 46 kind = Cl::CL_Function; 47 // No void either, but qualified void is OK because it is "other than void". 48 // Void "lvalues" are classified as addressable void values, which are void 49 // expressions whose address can be taken. 50 else if (TR->isVoidType() && !TR.hasQualifiers()) 51 kind = (kind == Cl::CL_LValue ? Cl::CL_AddressableVoid : Cl::CL_Void); 52 } 53 54 // Enable this assertion for testing. 55 switch (kind) { 56 case Cl::CL_LValue: assert(getValueKind() == VK_LValue); break; 57 case Cl::CL_XValue: assert(getValueKind() == VK_XValue); break; 58 case Cl::CL_Function: 59 case Cl::CL_Void: 60 case Cl::CL_AddressableVoid: 61 case Cl::CL_DuplicateVectorComponents: 62 case Cl::CL_MemberFunction: 63 case Cl::CL_SubObjCPropertySetting: 64 case Cl::CL_ClassTemporary: 65 case Cl::CL_ArrayTemporary: 66 case Cl::CL_ObjCMessageRValue: 67 case Cl::CL_PRValue: assert(getValueKind() == VK_RValue); break; 68 } 69 70 Cl::ModifiableType modifiable = Cl::CM_Untested; 71 if (Loc) 72 modifiable = IsModifiable(Ctx, this, kind, *Loc); 73 return Classification(kind, modifiable); 74} 75 76/// Classify an expression which creates a temporary, based on its type. 77static Cl::Kinds ClassifyTemporary(QualType T) { 78 if (T->isRecordType()) 79 return Cl::CL_ClassTemporary; 80 if (T->isArrayType()) 81 return Cl::CL_ArrayTemporary; 82 83 // No special classification: these don't behave differently from normal 84 // prvalues. 85 return Cl::CL_PRValue; 86} 87 88static Cl::Kinds ClassifyExprValueKind(const LangOptions &Lang, 89 const Expr *E, 90 ExprValueKind Kind) { 91 switch (Kind) { 92 case VK_RValue: 93 return Lang.CPlusPlus ? ClassifyTemporary(E->getType()) : Cl::CL_PRValue; 94 case VK_LValue: 95 return Cl::CL_LValue; 96 case VK_XValue: 97 return Cl::CL_XValue; 98 } 99 llvm_unreachable("Invalid value category of implicit cast."); 100} 101 102static Cl::Kinds ClassifyInternal(ASTContext &Ctx, const Expr *E) { 103 // This function takes the first stab at classifying expressions. 104 const LangOptions &Lang = Ctx.getLangOpts(); 105 106 switch (E->getStmtClass()) { 107 case Stmt::NoStmtClass: 108#define ABSTRACT_STMT(Kind) 109#define STMT(Kind, Base) case Expr::Kind##Class: 110#define EXPR(Kind, Base) 111#include "clang/AST/StmtNodes.inc" 112 llvm_unreachable("cannot classify a statement"); 113 114 // First come the expressions that are always lvalues, unconditionally. 115 case Expr::ObjCIsaExprClass: 116 // C++ [expr.prim.general]p1: A string literal is an lvalue. 117 case Expr::StringLiteralClass: 118 // @encode is equivalent to its string 119 case Expr::ObjCEncodeExprClass: 120 // __func__ and friends are too. 121 case Expr::PredefinedExprClass: 122 // Property references are lvalues 123 case Expr::ObjCSubscriptRefExprClass: 124 case Expr::ObjCPropertyRefExprClass: 125 // C++ [expr.typeid]p1: The result of a typeid expression is an lvalue of... 126 case Expr::CXXTypeidExprClass: 127 // Unresolved lookups get classified as lvalues. 128 // FIXME: Is this wise? Should they get their own kind? 129 case Expr::UnresolvedLookupExprClass: 130 case Expr::UnresolvedMemberExprClass: 131 case Expr::CXXDependentScopeMemberExprClass: 132 case Expr::DependentScopeDeclRefExprClass: 133 // ObjC instance variables are lvalues 134 // FIXME: ObjC++0x might have different rules 135 case Expr::ObjCIvarRefExprClass: 136 case Expr::FunctionParmPackExprClass: 137 case Expr::MSPropertyRefExprClass: 138 return Cl::CL_LValue; 139 140 // C99 6.5.2.5p5 says that compound literals are lvalues. 141 // In C++, they're prvalue temporaries. 142 case Expr::CompoundLiteralExprClass: 143 return Ctx.getLangOpts().CPlusPlus ? ClassifyTemporary(E->getType()) 144 : Cl::CL_LValue; 145 146 // Expressions that are prvalues. 147 case Expr::CXXBoolLiteralExprClass: 148 case Expr::CXXPseudoDestructorExprClass: 149 case Expr::UnaryExprOrTypeTraitExprClass: 150 case Expr::CXXNewExprClass: 151 case Expr::CXXThisExprClass: 152 case Expr::CXXNullPtrLiteralExprClass: 153 case Expr::ImaginaryLiteralClass: 154 case Expr::GNUNullExprClass: 155 case Expr::OffsetOfExprClass: 156 case Expr::CXXThrowExprClass: 157 case Expr::ShuffleVectorExprClass: 158 case Expr::ConvertVectorExprClass: 159 case Expr::IntegerLiteralClass: 160 case Expr::CharacterLiteralClass: 161 case Expr::AddrLabelExprClass: 162 case Expr::CXXDeleteExprClass: 163 case Expr::ImplicitValueInitExprClass: 164 case Expr::BlockExprClass: 165 case Expr::FloatingLiteralClass: 166 case Expr::CXXNoexceptExprClass: 167 case Expr::CXXScalarValueInitExprClass: 168 case Expr::UnaryTypeTraitExprClass: 169 case Expr::BinaryTypeTraitExprClass: 170 case Expr::TypeTraitExprClass: 171 case Expr::ArrayTypeTraitExprClass: 172 case Expr::ExpressionTraitExprClass: 173 case Expr::ObjCSelectorExprClass: 174 case Expr::ObjCProtocolExprClass: 175 case Expr::ObjCStringLiteralClass: 176 case Expr::ObjCBoxedExprClass: 177 case Expr::ObjCArrayLiteralClass: 178 case Expr::ObjCDictionaryLiteralClass: 179 case Expr::ObjCBoolLiteralExprClass: 180 case Expr::ParenListExprClass: 181 case Expr::SizeOfPackExprClass: 182 case Expr::SubstNonTypeTemplateParmPackExprClass: 183 case Expr::AsTypeExprClass: 184 case Expr::ObjCIndirectCopyRestoreExprClass: 185 case Expr::AtomicExprClass: 186 return Cl::CL_PRValue; 187 188 // Next come the complicated cases. 189 case Expr::SubstNonTypeTemplateParmExprClass: 190 return ClassifyInternal(Ctx, 191 cast<SubstNonTypeTemplateParmExpr>(E)->getReplacement()); 192 193 // C++ [expr.sub]p1: The result is an lvalue of type "T". 194 // However, subscripting vector types is more like member access. 195 case Expr::ArraySubscriptExprClass: 196 if (cast<ArraySubscriptExpr>(E)->getBase()->getType()->isVectorType()) 197 return ClassifyInternal(Ctx, cast<ArraySubscriptExpr>(E)->getBase()); 198 return Cl::CL_LValue; 199 200 // C++ [expr.prim.general]p3: The result is an lvalue if the entity is a 201 // function or variable and a prvalue otherwise. 202 case Expr::DeclRefExprClass: 203 if (E->getType() == Ctx.UnknownAnyTy) 204 return isa<FunctionDecl>(cast<DeclRefExpr>(E)->getDecl()) 205 ? Cl::CL_PRValue : Cl::CL_LValue; 206 return ClassifyDecl(Ctx, cast<DeclRefExpr>(E)->getDecl()); 207 208 // Member access is complex. 209 case Expr::MemberExprClass: 210 return ClassifyMemberExpr(Ctx, cast<MemberExpr>(E)); 211 212 case Expr::UnaryOperatorClass: 213 switch (cast<UnaryOperator>(E)->getOpcode()) { 214 // C++ [expr.unary.op]p1: The unary * operator performs indirection: 215 // [...] the result is an lvalue referring to the object or function 216 // to which the expression points. 217 case UO_Deref: 218 return Cl::CL_LValue; 219 220 // GNU extensions, simply look through them. 221 case UO_Extension: 222 return ClassifyInternal(Ctx, cast<UnaryOperator>(E)->getSubExpr()); 223 224 // Treat _Real and _Imag basically as if they were member 225 // expressions: l-value only if the operand is a true l-value. 226 case UO_Real: 227 case UO_Imag: { 228 const Expr *Op = cast<UnaryOperator>(E)->getSubExpr()->IgnoreParens(); 229 Cl::Kinds K = ClassifyInternal(Ctx, Op); 230 if (K != Cl::CL_LValue) return K; 231 232 if (isa<ObjCPropertyRefExpr>(Op)) 233 return Cl::CL_SubObjCPropertySetting; 234 return Cl::CL_LValue; 235 } 236 237 // C++ [expr.pre.incr]p1: The result is the updated operand; it is an 238 // lvalue, [...] 239 // Not so in C. 240 case UO_PreInc: 241 case UO_PreDec: 242 return Lang.CPlusPlus ? Cl::CL_LValue : Cl::CL_PRValue; 243 244 default: 245 return Cl::CL_PRValue; 246 } 247 248 case Expr::OpaqueValueExprClass: 249 return ClassifyExprValueKind(Lang, E, E->getValueKind()); 250 251 // Pseudo-object expressions can produce l-values with reference magic. 252 case Expr::PseudoObjectExprClass: 253 return ClassifyExprValueKind(Lang, E, 254 cast<PseudoObjectExpr>(E)->getValueKind()); 255 256 // Implicit casts are lvalues if they're lvalue casts. Other than that, we 257 // only specifically record class temporaries. 258 case Expr::ImplicitCastExprClass: 259 return ClassifyExprValueKind(Lang, E, E->getValueKind()); 260 261 // C++ [expr.prim.general]p4: The presence of parentheses does not affect 262 // whether the expression is an lvalue. 263 case Expr::ParenExprClass: 264 return ClassifyInternal(Ctx, cast<ParenExpr>(E)->getSubExpr()); 265 266 // C11 6.5.1.1p4: [A generic selection] is an lvalue, a function designator, 267 // or a void expression if its result expression is, respectively, an 268 // lvalue, a function designator, or a void expression. 269 case Expr::GenericSelectionExprClass: 270 if (cast<GenericSelectionExpr>(E)->isResultDependent()) 271 return Cl::CL_PRValue; 272 return ClassifyInternal(Ctx,cast<GenericSelectionExpr>(E)->getResultExpr()); 273 274 case Expr::BinaryOperatorClass: 275 case Expr::CompoundAssignOperatorClass: 276 // C doesn't have any binary expressions that are lvalues. 277 if (Lang.CPlusPlus) 278 return ClassifyBinaryOp(Ctx, cast<BinaryOperator>(E)); 279 return Cl::CL_PRValue; 280 281 case Expr::CallExprClass: 282 case Expr::CXXOperatorCallExprClass: 283 case Expr::CXXMemberCallExprClass: 284 case Expr::UserDefinedLiteralClass: 285 case Expr::CUDAKernelCallExprClass: 286 return ClassifyUnnamed(Ctx, cast<CallExpr>(E)->getCallReturnType()); 287 288 // __builtin_choose_expr is equivalent to the chosen expression. 289 case Expr::ChooseExprClass: 290 return ClassifyInternal(Ctx, cast<ChooseExpr>(E)->getChosenSubExpr()); 291 292 // Extended vector element access is an lvalue unless there are duplicates 293 // in the shuffle expression. 294 case Expr::ExtVectorElementExprClass: 295 if (cast<ExtVectorElementExpr>(E)->containsDuplicateElements()) 296 return Cl::CL_DuplicateVectorComponents; 297 if (cast<ExtVectorElementExpr>(E)->isArrow()) 298 return Cl::CL_LValue; 299 return ClassifyInternal(Ctx, cast<ExtVectorElementExpr>(E)->getBase()); 300 301 // Simply look at the actual default argument. 302 case Expr::CXXDefaultArgExprClass: 303 return ClassifyInternal(Ctx, cast<CXXDefaultArgExpr>(E)->getExpr()); 304 305 // Same idea for default initializers. 306 case Expr::CXXDefaultInitExprClass: 307 return ClassifyInternal(Ctx, cast<CXXDefaultInitExpr>(E)->getExpr()); 308 309 // Same idea for temporary binding. 310 case Expr::CXXBindTemporaryExprClass: 311 return ClassifyInternal(Ctx, cast<CXXBindTemporaryExpr>(E)->getSubExpr()); 312 313 // And the cleanups guard. 314 case Expr::ExprWithCleanupsClass: 315 return ClassifyInternal(Ctx, cast<ExprWithCleanups>(E)->getSubExpr()); 316 317 // Casts depend completely on the target type. All casts work the same. 318 case Expr::CStyleCastExprClass: 319 case Expr::CXXFunctionalCastExprClass: 320 case Expr::CXXStaticCastExprClass: 321 case Expr::CXXDynamicCastExprClass: 322 case Expr::CXXReinterpretCastExprClass: 323 case Expr::CXXConstCastExprClass: 324 case Expr::ObjCBridgedCastExprClass: 325 // Only in C++ can casts be interesting at all. 326 if (!Lang.CPlusPlus) return Cl::CL_PRValue; 327 return ClassifyUnnamed(Ctx, cast<ExplicitCastExpr>(E)->getTypeAsWritten()); 328 329 case Expr::CXXUnresolvedConstructExprClass: 330 return ClassifyUnnamed(Ctx, 331 cast<CXXUnresolvedConstructExpr>(E)->getTypeAsWritten()); 332 333 case Expr::BinaryConditionalOperatorClass: { 334 if (!Lang.CPlusPlus) return Cl::CL_PRValue; 335 const BinaryConditionalOperator *co = cast<BinaryConditionalOperator>(E); 336 return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr()); 337 } 338 339 case Expr::ConditionalOperatorClass: { 340 // Once again, only C++ is interesting. 341 if (!Lang.CPlusPlus) return Cl::CL_PRValue; 342 const ConditionalOperator *co = cast<ConditionalOperator>(E); 343 return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr()); 344 } 345 346 // ObjC message sends are effectively function calls, if the target function 347 // is known. 348 case Expr::ObjCMessageExprClass: 349 if (const ObjCMethodDecl *Method = 350 cast<ObjCMessageExpr>(E)->getMethodDecl()) { 351 Cl::Kinds kind = ClassifyUnnamed(Ctx, Method->getResultType()); 352 return (kind == Cl::CL_PRValue) ? Cl::CL_ObjCMessageRValue : kind; 353 } 354 return Cl::CL_PRValue; 355 356 // Some C++ expressions are always class temporaries. 357 case Expr::CXXConstructExprClass: 358 case Expr::CXXTemporaryObjectExprClass: 359 case Expr::LambdaExprClass: 360 case Expr::CXXStdInitializerListExprClass: 361 return Cl::CL_ClassTemporary; 362 363 case Expr::VAArgExprClass: 364 return ClassifyUnnamed(Ctx, E->getType()); 365 366 case Expr::DesignatedInitExprClass: 367 return ClassifyInternal(Ctx, cast<DesignatedInitExpr>(E)->getInit()); 368 369 case Expr::StmtExprClass: { 370 const CompoundStmt *S = cast<StmtExpr>(E)->getSubStmt(); 371 if (const Expr *LastExpr = dyn_cast_or_null<Expr>(S->body_back())) 372 return ClassifyUnnamed(Ctx, LastExpr->getType()); 373 return Cl::CL_PRValue; 374 } 375 376 case Expr::CXXUuidofExprClass: 377 return Cl::CL_LValue; 378 379 case Expr::PackExpansionExprClass: 380 return ClassifyInternal(Ctx, cast<PackExpansionExpr>(E)->getPattern()); 381 382 case Expr::MaterializeTemporaryExprClass: 383 return cast<MaterializeTemporaryExpr>(E)->isBoundToLvalueReference() 384 ? Cl::CL_LValue 385 : Cl::CL_XValue; 386 387 case Expr::InitListExprClass: 388 // An init list can be an lvalue if it is bound to a reference and 389 // contains only one element. In that case, we look at that element 390 // for an exact classification. Init list creation takes care of the 391 // value kind for us, so we only need to fine-tune. 392 if (E->isRValue()) 393 return ClassifyExprValueKind(Lang, E, E->getValueKind()); 394 assert(cast<InitListExpr>(E)->getNumInits() == 1 && 395 "Only 1-element init lists can be glvalues."); 396 return ClassifyInternal(Ctx, cast<InitListExpr>(E)->getInit(0)); 397 } 398 399 llvm_unreachable("unhandled expression kind in classification"); 400} 401 402/// ClassifyDecl - Return the classification of an expression referencing the 403/// given declaration. 404static Cl::Kinds ClassifyDecl(ASTContext &Ctx, const Decl *D) { 405 // C++ [expr.prim.general]p6: The result is an lvalue if the entity is a 406 // function, variable, or data member and a prvalue otherwise. 407 // In C, functions are not lvalues. 408 // In addition, NonTypeTemplateParmDecl derives from VarDecl but isn't an 409 // lvalue unless it's a reference type (C++ [temp.param]p6), so we need to 410 // special-case this. 411 412 if (isa<CXXMethodDecl>(D) && cast<CXXMethodDecl>(D)->isInstance()) 413 return Cl::CL_MemberFunction; 414 415 bool islvalue; 416 if (const NonTypeTemplateParmDecl *NTTParm = 417 dyn_cast<NonTypeTemplateParmDecl>(D)) 418 islvalue = NTTParm->getType()->isReferenceType(); 419 else 420 islvalue = isa<VarDecl>(D) || isa<FieldDecl>(D) || 421 isa<IndirectFieldDecl>(D) || 422 (Ctx.getLangOpts().CPlusPlus && 423 (isa<FunctionDecl>(D) || isa<FunctionTemplateDecl>(D))); 424 425 return islvalue ? Cl::CL_LValue : Cl::CL_PRValue; 426} 427 428/// ClassifyUnnamed - Return the classification of an expression yielding an 429/// unnamed value of the given type. This applies in particular to function 430/// calls and casts. 431static Cl::Kinds ClassifyUnnamed(ASTContext &Ctx, QualType T) { 432 // In C, function calls are always rvalues. 433 if (!Ctx.getLangOpts().CPlusPlus) return Cl::CL_PRValue; 434 435 // C++ [expr.call]p10: A function call is an lvalue if the result type is an 436 // lvalue reference type or an rvalue reference to function type, an xvalue 437 // if the result type is an rvalue reference to object type, and a prvalue 438 // otherwise. 439 if (T->isLValueReferenceType()) 440 return Cl::CL_LValue; 441 const RValueReferenceType *RV = T->getAs<RValueReferenceType>(); 442 if (!RV) // Could still be a class temporary, though. 443 return ClassifyTemporary(T); 444 445 return RV->getPointeeType()->isFunctionType() ? Cl::CL_LValue : Cl::CL_XValue; 446} 447 448static Cl::Kinds ClassifyMemberExpr(ASTContext &Ctx, const MemberExpr *E) { 449 if (E->getType() == Ctx.UnknownAnyTy) 450 return (isa<FunctionDecl>(E->getMemberDecl()) 451 ? Cl::CL_PRValue : Cl::CL_LValue); 452 453 // Handle C first, it's easier. 454 if (!Ctx.getLangOpts().CPlusPlus) { 455 // C99 6.5.2.3p3 456 // For dot access, the expression is an lvalue if the first part is. For 457 // arrow access, it always is an lvalue. 458 if (E->isArrow()) 459 return Cl::CL_LValue; 460 // ObjC property accesses are not lvalues, but get special treatment. 461 Expr *Base = E->getBase()->IgnoreParens(); 462 if (isa<ObjCPropertyRefExpr>(Base)) 463 return Cl::CL_SubObjCPropertySetting; 464 return ClassifyInternal(Ctx, Base); 465 } 466 467 NamedDecl *Member = E->getMemberDecl(); 468 // C++ [expr.ref]p3: E1->E2 is converted to the equivalent form (*(E1)).E2. 469 // C++ [expr.ref]p4: If E2 is declared to have type "reference to T", then 470 // E1.E2 is an lvalue. 471 if (ValueDecl *Value = dyn_cast<ValueDecl>(Member)) 472 if (Value->getType()->isReferenceType()) 473 return Cl::CL_LValue; 474 475 // Otherwise, one of the following rules applies. 476 // -- If E2 is a static member [...] then E1.E2 is an lvalue. 477 if (isa<VarDecl>(Member) && Member->getDeclContext()->isRecord()) 478 return Cl::CL_LValue; 479 480 // -- If E2 is a non-static data member [...]. If E1 is an lvalue, then 481 // E1.E2 is an lvalue; if E1 is an xvalue, then E1.E2 is an xvalue; 482 // otherwise, it is a prvalue. 483 if (isa<FieldDecl>(Member)) { 484 // *E1 is an lvalue 485 if (E->isArrow()) 486 return Cl::CL_LValue; 487 Expr *Base = E->getBase()->IgnoreParenImpCasts(); 488 if (isa<ObjCPropertyRefExpr>(Base)) 489 return Cl::CL_SubObjCPropertySetting; 490 return ClassifyInternal(Ctx, E->getBase()); 491 } 492 493 // -- If E2 is a [...] member function, [...] 494 // -- If it refers to a static member function [...], then E1.E2 is an 495 // lvalue; [...] 496 // -- Otherwise [...] E1.E2 is a prvalue. 497 if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(Member)) 498 return Method->isStatic() ? Cl::CL_LValue : Cl::CL_MemberFunction; 499 500 // -- If E2 is a member enumerator [...], the expression E1.E2 is a prvalue. 501 // So is everything else we haven't handled yet. 502 return Cl::CL_PRValue; 503} 504 505static Cl::Kinds ClassifyBinaryOp(ASTContext &Ctx, const BinaryOperator *E) { 506 assert(Ctx.getLangOpts().CPlusPlus && 507 "This is only relevant for C++."); 508 // C++ [expr.ass]p1: All [...] return an lvalue referring to the left operand. 509 // Except we override this for writes to ObjC properties. 510 if (E->isAssignmentOp()) 511 return (E->getLHS()->getObjectKind() == OK_ObjCProperty 512 ? Cl::CL_PRValue : Cl::CL_LValue); 513 514 // C++ [expr.comma]p1: the result is of the same value category as its right 515 // operand, [...]. 516 if (E->getOpcode() == BO_Comma) 517 return ClassifyInternal(Ctx, E->getRHS()); 518 519 // C++ [expr.mptr.oper]p6: The result of a .* expression whose second operand 520 // is a pointer to a data member is of the same value category as its first 521 // operand. 522 if (E->getOpcode() == BO_PtrMemD) 523 return (E->getType()->isFunctionType() || 524 E->hasPlaceholderType(BuiltinType::BoundMember)) 525 ? Cl::CL_MemberFunction 526 : ClassifyInternal(Ctx, E->getLHS()); 527 528 // C++ [expr.mptr.oper]p6: The result of an ->* expression is an lvalue if its 529 // second operand is a pointer to data member and a prvalue otherwise. 530 if (E->getOpcode() == BO_PtrMemI) 531 return (E->getType()->isFunctionType() || 532 E->hasPlaceholderType(BuiltinType::BoundMember)) 533 ? Cl::CL_MemberFunction 534 : Cl::CL_LValue; 535 536 // All other binary operations are prvalues. 537 return Cl::CL_PRValue; 538} 539 540static Cl::Kinds ClassifyConditional(ASTContext &Ctx, const Expr *True, 541 const Expr *False) { 542 assert(Ctx.getLangOpts().CPlusPlus && 543 "This is only relevant for C++."); 544 545 // C++ [expr.cond]p2 546 // If either the second or the third operand has type (cv) void, [...] 547 // the result [...] is a prvalue. 548 if (True->getType()->isVoidType() || False->getType()->isVoidType()) 549 return Cl::CL_PRValue; 550 551 // Note that at this point, we have already performed all conversions 552 // according to [expr.cond]p3. 553 // C++ [expr.cond]p4: If the second and third operands are glvalues of the 554 // same value category [...], the result is of that [...] value category. 555 // C++ [expr.cond]p5: Otherwise, the result is a prvalue. 556 Cl::Kinds LCl = ClassifyInternal(Ctx, True), 557 RCl = ClassifyInternal(Ctx, False); 558 return LCl == RCl ? LCl : Cl::CL_PRValue; 559} 560 561static Cl::ModifiableType IsModifiable(ASTContext &Ctx, const Expr *E, 562 Cl::Kinds Kind, SourceLocation &Loc) { 563 // As a general rule, we only care about lvalues. But there are some rvalues 564 // for which we want to generate special results. 565 if (Kind == Cl::CL_PRValue) { 566 // For the sake of better diagnostics, we want to specifically recognize 567 // use of the GCC cast-as-lvalue extension. 568 if (const ExplicitCastExpr *CE = 569 dyn_cast<ExplicitCastExpr>(E->IgnoreParens())) { 570 if (CE->getSubExpr()->IgnoreParenImpCasts()->isLValue()) { 571 Loc = CE->getExprLoc(); 572 return Cl::CM_LValueCast; 573 } 574 } 575 } 576 if (Kind != Cl::CL_LValue) 577 return Cl::CM_RValue; 578 579 // This is the lvalue case. 580 // Functions are lvalues in C++, but not modifiable. (C++ [basic.lval]p6) 581 if (Ctx.getLangOpts().CPlusPlus && E->getType()->isFunctionType()) 582 return Cl::CM_Function; 583 584 // Assignment to a property in ObjC is an implicit setter access. But a 585 // setter might not exist. 586 if (const ObjCPropertyRefExpr *Expr = dyn_cast<ObjCPropertyRefExpr>(E)) { 587 if (Expr->isImplicitProperty() && Expr->getImplicitPropertySetter() == 0) 588 return Cl::CM_NoSetterProperty; 589 } 590 591 CanQualType CT = Ctx.getCanonicalType(E->getType()); 592 // Const stuff is obviously not modifiable. 593 if (CT.isConstQualified()) 594 return Cl::CM_ConstQualified; 595 if (CT.getQualifiers().getAddressSpace() == LangAS::opencl_constant) 596 return Cl::CM_ConstQualified; 597 598 // Arrays are not modifiable, only their elements are. 599 if (CT->isArrayType()) 600 return Cl::CM_ArrayType; 601 // Incomplete types are not modifiable. 602 if (CT->isIncompleteType()) 603 return Cl::CM_IncompleteType; 604 605 // Records with any const fields (recursively) are not modifiable. 606 if (const RecordType *R = CT->getAs<RecordType>()) { 607 assert((E->getObjectKind() == OK_ObjCProperty || 608 !Ctx.getLangOpts().CPlusPlus) && 609 "C++ struct assignment should be resolved by the " 610 "copy assignment operator."); 611 if (R->hasConstFields()) 612 return Cl::CM_ConstQualified; 613 } 614 615 return Cl::CM_Modifiable; 616} 617 618Expr::LValueClassification Expr::ClassifyLValue(ASTContext &Ctx) const { 619 Classification VC = Classify(Ctx); 620 switch (VC.getKind()) { 621 case Cl::CL_LValue: return LV_Valid; 622 case Cl::CL_XValue: return LV_InvalidExpression; 623 case Cl::CL_Function: return LV_NotObjectType; 624 case Cl::CL_Void: return LV_InvalidExpression; 625 case Cl::CL_AddressableVoid: return LV_IncompleteVoidType; 626 case Cl::CL_DuplicateVectorComponents: return LV_DuplicateVectorComponents; 627 case Cl::CL_MemberFunction: return LV_MemberFunction; 628 case Cl::CL_SubObjCPropertySetting: return LV_SubObjCPropertySetting; 629 case Cl::CL_ClassTemporary: return LV_ClassTemporary; 630 case Cl::CL_ArrayTemporary: return LV_ArrayTemporary; 631 case Cl::CL_ObjCMessageRValue: return LV_InvalidMessageExpression; 632 case Cl::CL_PRValue: return LV_InvalidExpression; 633 } 634 llvm_unreachable("Unhandled kind"); 635} 636 637Expr::isModifiableLvalueResult 638Expr::isModifiableLvalue(ASTContext &Ctx, SourceLocation *Loc) const { 639 SourceLocation dummy; 640 Classification VC = ClassifyModifiable(Ctx, Loc ? *Loc : dummy); 641 switch (VC.getKind()) { 642 case Cl::CL_LValue: break; 643 case Cl::CL_XValue: return MLV_InvalidExpression; 644 case Cl::CL_Function: return MLV_NotObjectType; 645 case Cl::CL_Void: return MLV_InvalidExpression; 646 case Cl::CL_AddressableVoid: return MLV_IncompleteVoidType; 647 case Cl::CL_DuplicateVectorComponents: return MLV_DuplicateVectorComponents; 648 case Cl::CL_MemberFunction: return MLV_MemberFunction; 649 case Cl::CL_SubObjCPropertySetting: return MLV_SubObjCPropertySetting; 650 case Cl::CL_ClassTemporary: return MLV_ClassTemporary; 651 case Cl::CL_ArrayTemporary: return MLV_ArrayTemporary; 652 case Cl::CL_ObjCMessageRValue: return MLV_InvalidMessageExpression; 653 case Cl::CL_PRValue: 654 return VC.getModifiable() == Cl::CM_LValueCast ? 655 MLV_LValueCast : MLV_InvalidExpression; 656 } 657 assert(VC.getKind() == Cl::CL_LValue && "Unhandled kind"); 658 switch (VC.getModifiable()) { 659 case Cl::CM_Untested: llvm_unreachable("Did not test modifiability"); 660 case Cl::CM_Modifiable: return MLV_Valid; 661 case Cl::CM_RValue: llvm_unreachable("CM_RValue and CL_LValue don't match"); 662 case Cl::CM_Function: return MLV_NotObjectType; 663 case Cl::CM_LValueCast: 664 llvm_unreachable("CM_LValueCast and CL_LValue don't match"); 665 case Cl::CM_NoSetterProperty: return MLV_NoSetterProperty; 666 case Cl::CM_ConstQualified: return MLV_ConstQualified; 667 case Cl::CM_ArrayType: return MLV_ArrayType; 668 case Cl::CM_IncompleteType: return MLV_IncompleteType; 669 } 670 llvm_unreachable("Unhandled modifiable type"); 671} 672